1. Field of the Invention
The present invention relates to an antenna structure for a TPMS (Tire pressure Monitoring System) transmitter to effectively increase the length of antenna and enhance the efficiency.
2. Description of the Prior Art
After a vehicle has driven for a time or been solarized and been low temperature at night, the vehicle easily produce the leak pressure to cause the pressure value lower the standard. As far as the driving safe is concerned, the leak pressure has the latent danger especial for high speed to break due to the tire pressure not enough, for example.
A prior TMPS transmitter includes a transmitter and a receiver set on or around the appearance of bearing to observe the signal form the transmitter set in the tire any time and to understand the pressure and temperature condition of tire. However, as far as the transmitter is concerned, the main types are internal transmitter and external transmitter, wherein the internal transmitter usually is set in the tire and fixed on the tire frame and the external transmitter set on the valve outside the tire. The module main includes an antenna, a transmitter IC, a micro-processor, a temperature and pressure sensor and a battery shown as in FIG. 1a. 
However, the framework, which is the antenna structure in printed circuit board (PCB) shown as the FIG. 1b, the antenna 11 needs to solder in PCB 10 directly. In order to avoid the antenna arm excessive long to snap by shaking or solder joint loosing, the antenna can be only designed in short shape; however, the design of short antenna is not only not convenient to fabricate but also easy to be short or interference with other electrical components. Besides, the weak intensity signal of short antenna easily causes the receiver error erroneous judgment to affect the driving safe. Moreover, the weak intensity signal needs higher power consumption to enhance the intensity of wireless signal, but that shortens the lifetime of battery.
Another prior art shown as in FIG. 1c, the antenna 11 is directly printed in circuit board 10. The method solves the issue of the intensity of antenna structure, but the loop antenna needs a bigger area of antenna's radiator and a whole ground-clearance area to expect effective radiation. Therefore, the transmitter of antenna structure has the issue of too big size.